The present invention is concerned with the production of porous hydratable protein food products having a texture and appearance similar to the muscle and tissue protein found in meats or fowl. More particularly this invention relates to a method for producing a fat containing expanded proteinaceous composition by working and heat extrusion of a mixture of proteinaceous material, fat, a non-proteinaceous and non-farinaceous filler, and sulfur and/or a sulfur compound.
There is a major effort in the world today to produce nutritious, high protein meat substitute products for both animal and human consumption. A significant effort has been directed toward the utilization of protein flours and meals derived from oil seed such as soy beans, peanuts, cottonseeds, and the like as raw materials in the production of said products. Recent developments in this area have focused on the production of meat-like protein products produced by extrusion or otherwise heat treating soy protein. For example, U.S. Pat. No. 3,537,859 discloses a method for preparing protein food products simulating bacon in texture by extruding a homogeneous mixture of defatted soy meal, fat, water and flavoring. The extrudate is characterized as non-expanded and contains entrained moisture of fat. U.S. Pat. No. 3,488,770 deals with a method for preparing an expanded porous protein food product having an open cell structure wherein a mixture comprising defatted soy meal and water is masticated at temperatures above about 250.degree. F and extruded from a zone of high pressure into a zone of lower pressure. The product is characterized as having a meat-like fibrous structure when hydrated. U.S. Pat. No. 3,496,858 discloses the preparation of an expanded protein product similar to the above except sulfur or a sulfur compound is added to the defatted soy meal prior to extrusion. These sulfur additives chemically interact with the protein molecules during processing giving rise to an extrudate having a high degree of expansion and very desirable fibrous structure.
Protein processed according to the teachings of the latter two patents discussed above does indeed have a texture and fibrous structure closely resembling meat. However, most meat products such as beef, poultry, lamp and pork contain a fat content varying from about 5 to 30% or more depending on the type and cut of meat. Much of this fat remains in the meat even after cooking and it is this fat which contributes to the smooth texture, nutrition, juicyness and pleasing organoleptic qualities associated with good quality cooked meats. Thus, it would be most desirable to produce a simulated meat product based on expanded proteinaceous materials which contains a certain amount of fat or oil in intimate association with the fibrous protein structure of the expanded protein.
Prior art workers have discovered that the presence of significant amounts of a fat or oil in the proteinaceous material to be extruded severely interferes with expansion of the extrudate and the formation of a fibrous structure. As a result, it is recommended that the protein material be substantially free of oil and that no fat be added to the proteinaceous material prior to extrusion.
It has been suggested by the prior art that fat or oil may be combined with the expanded proteinaceous meat substitute after extrusion by coating, impregnating or otherwise infusing the material with a liquid fat. Note, for example, British Pat. No. 1,225,557. However, it is most difficult by such techniques to obtain the intimate association of protein and carbohydrate as is found in real meat products, and the fat will often settle out within short periods of time severly detracting from product palatability.